Thursday, 20 July 2006

If your attention is elsewhere you can miss something right in front of your eyes – a phenomenon that’s been dubbed ‘inattentional blindness’. For example, witnesses confronted by an armed attacker sometimes fail to remember anything else about the assailant apart from their weapon, so preoccupied were they by the knife or gun. Now Seema Clifasefi and colleagues report that just one stiff drink can exaggerate inattentional blindness, a finding they argue justifies the setting of a lower legal alcohol driving limit.

Forty-seven students watched a short video clip of two teams passing a basketball between their respective team members. The participants’ task was to count the number of passes made by one of the teams. During the clip, a woman in a gorilla suit runs between the players and beats her chest. Crucially, when asked afterwards, only 18 per cent of the students given a drink of vodka and tonic said they’d noticed the woman, compared with 46 per cent of the students given a drink of plain tonic water.

Alcohol clearly exaggerated the inattentional blindness that was also experienced by many of the sober students.

This wasn’t a placebo effect – half the students given plain tonic water were told they had been given vodka, and yet 42 per cent of them noticed the gorilla woman. By contrast, half the students given vodka were told they’d been given tonic water, and yet only 18 per cent of them noticed the gorilla. The alcohol seems to have had a direct effect on the participants’ cognition.

“Even at only half the legal driving limit in the US, our subjects were at significantly increased risk of failing to notice an unexpected object compared with their sober counterparts. In light of this result, perhaps lawmakers should reconsider the level of intoxication deemed legal to operate a vehicle”, the researchers concluded.
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Was the experiment controlled for priming? How do you know that everyone was doing what you asked and focusing on the counting? Was the taste of the alcohol disguised? Surely someone told they were recieving tonic and getting vodka would notice the difference! 47 participants is not really enough to warrant interesting findings? Having said all that I do think with more research to back it up this point would be proved. But perhaps not for all. I would not drive after one drink because I can feel my judgement is impaired. But, other people have more tolerance....possibly??

Here are a few more details that might answer some of the questions that have been raised. Participants were screened before the experiment for medical conditions, pregnancy, drinking problems etc and were excluded if any of these were positive.

Participants were asked how intoxicated they felt (based on their agreement with statements like 'my head felt fuzzy') - those told they had been given alcohol reported feeling more intoxicated than those told they had been given tonic water, suggesting the placebo effect worked.

Those participants given alcohol were given a dose proportionate to their body weight.

There were four groups - those given alcohol who were told they had been given alcohol; those given alcohol told they had been given tonic water; those given tonic water but told they'd been given alcohol; and those given tonic water and told they'd been given tonic water. This design allowed the researchers to distinguish between the psychological or placebo effects of believing one has drunk alcohol and the actual physical effects of alcohol on one's cognition. The results suggest alcohol exacerbates inattentional blindness, not because of a placebo effect, but because of its effect on the brain.